Per The Font of All Wisdom and Knowledge:The AP college football poll's origins go back to the 1930s. The news media began running their own polls of sports writers to determine, by popular opinion, the best college football teams in the country. One of the earliest such polls was conducted by the AP in November 1934. In 1935, AP sports editor Alan J. Gould declared a three-way tie for national champion in football between Minnesota, Princeton, and Southern Methodist. Minnesota fans protested and a number of Gould's colleagues led by Charles "Cy" Sherman suggested he create a poll of sports editors instead of only using his own list. The next year the weekly AP college football poll was born, and has run continuously from 1936.
Due to the long-standing historical ties between individual college football conferences and high-paying bowl games like the Rose Bowl and Orange Bowl, the NCAA had not held a tournament or championship game to determine the national champion of what is now the highest division, NCAA Division I, Football Bowl Subdivision (the Division I, Football Championship Subdivision and lower divisions do hold championship tournaments). As a result, the public and the media began to acknowledge the leading vote-getter in the final AP poll as the national champion for that season.
While the AP poll currently lists the Top 25 teams in the nation, from 1936 to 1988, the wire service only ranked twenty teams, except from 1961 to 1967, when only ten teams were recognized. The AP expanded to the current 25 teams in 1989.
The AP began conducting a preseason poll in 1950.
At the end of the 1947 season, the AP released an unofficial post-bowl poll which differed from the regular season final poll. Until the 1968 college football season, the final AP poll of the season was released following the end of the regular season, with the lone exception of the 1965 season. In 1964, Alabama was named the national champion in the final AP Poll following the completion of the regular season, but lost in the Orange Bowl to Texas, leaving Arkansas as the only undefeated, untied team after the Razorbacks defeated Nebraska in the Cotton Bowl. In 1965, the AP's decision to wait to crown its champion paid handsomely, as top-ranked Michigan State lost to UCLA in the Rose Bowl, number two Arkansas lost to LSU in the Cotton Bowl, and fourth-ranked Alabama defeated third-ranked Nebraska in the Orange Bowl, vaulting the Crimson Tide to the top of the AP's final poll (Michigan State was named national champion in the final UPI Coaches Poll, which did not conduct a post-bowl poll).
Beginning in 1968, the post bowl game poll became permanent and the AP championship reflected the bowl game results. The UPI did not follow suit with the coaches' poll until the 1974 season.
https://en.wikipedia.org/wiki/AP_poll
